Typically, automotive wheel manufacturers have attempted to form the same axle for a center-pilot opening and an axle and to a tire rim bead seat to manufacture a wheel which may be perfectly coupled to the axle in the same axle.
Even if the tire wheel is precisely manufactured as above, the coupling of the tire wheel and the axle of the vehicle is conducted by inserting a plurality of stud bolts installed through hub and drum of axle to a fixing hole of the wheel and then by coupling the stud bolts and nuts. During the foregoing process, the center of the wheel does not conform to the center of the axle due to the difference of diameters of the stud bolts and the fixing hole formed in the tire wheel.
If the vehicle is braked while driving, heat is generated from a friction force between a brake drum or disc and pad. The heat generated therefrom is transferred to stud bolts, brake drum and wheel.
During the heat transfer process, parts have their own thermal expansion coefficient and thus vary the amount of thermal expansion. Such variation in thermal expansion causes change in the coupling and supporting state of the wheel with respect to the axle, and adversely affects the driving and ends in a failure to maintain structural stability ensured at the time of designing a vehicle.
Failure to ensure conformity between the center of the axle and the center of the tire wheel causes a relative movement of the drum and wheel having the stud bolt as a result of great load to the axle by large trucks or buses. Further, a frictional movement between a disc and nut of the tire wheel is caused and the nut is disconnected from the stud bolt or fixed thereto. Accordingly, fastening bolts is performed repeatedly after driving certain distance (approximately 100 km) at the time of ex-mill or of replacing tires.
Japanese Patent Publications nos. 07-228101 and 05-27840 disclose technical configurations to match the axle to the center of the wheel.
A conventional configuration for preventing unfastening of a wheel nut includes a first stud bolt which is inserted into a drum through an internal wheel, a wheel conical ring and flange interposed between the internal wheel and the flange of a hub from an external wheel while a brake drum, external and internal wheels and hub are assembled; a second stud bolt which is inserted into a core on the external wheel of the first stud bolt through a coupling hole of the internal and external wheels; and a wheel nut which is inserted into an external screw of the second stud bolt.
The foregoing configuration includes two members in which the stud bolt is coupled to the nut, and thus structural stability is not ensured. If the first and second bolts are unfastened, the wheel is not firmly fixed, and the thermal expansion issue may not be solved fundamentally.
In particular, each part of an assembly including a brake unit has different degrees of contact to an external device, and thermal parallel is not achieved easily. Accordingly, thermal expansion of the drum, stud bolt and wheel vary by repeated braking, and such variation distorts the wheel assembly.
The distortion of the wheel assembly causes uneven wear, one side brake and worsens steering performance according to driving.
The present applicant has filed application for a ring which prevents distortion of an axle and wheel of a vehicle, and filed application for this invention after continuous research and development.